MEDUS-B. I. 



vessel. About 32 fairly long tentacles. 8 marginal vesicles, each containing 3 4 or more concretions Velum well developed. 

 Manubrium, gonads, and tentacular bulbs yellowish or reddish-brown. 



This diagnosis is based on specimens, examined bv me at Plymouth, :.nd it differs in certain regards from that given 



bv Mayer. 



The corresponding hydroid is Campanulhia rfp.ns Hincks. 



The medusa is common off the coasts of Great Britain and Ilolhmd 



Genus Phialidium lAiickarl. 

 Phialidium hemisphaericum (Cronovius). 



Plate IV, fig. 14; Plate \", fig. 3. Textfigs. 16 and 17. 

 Medusa hemispJurrica Gronoviu.s 1760. Observationes de animalciilis . . . Acta Helvetica. \'ol. I\'. — p. 35. 

 Thaumantias Iiciiiisplurrica Forbes 1848. Hritisli Naked-eyed Medu.sie. - ]). 49. 

 i. p. Phiali'di'iiiii variahilc Haeckel 1879. Sy.steni der Medu.sen. — p. 186. 



Phi'altdiiiui ti-iiipoynrinut Browne 1896. Ou British Hydroids and Medusa;. — Proceed. Zool. Soc. Lon- 

 don. — p. 489. Plate X\ai, figs. 4, 5, 6. 

 — Iieinispliicricniii Mayer 1910. Medusae of the World. — p. 266. 



For further synonymy, see Browne 1896 and Mayer 1910. 



Bell nearly hemispherical, 20 — 25 mm wide; gelatinous substance thin. Manubrium small, with 

 4 .simple lips. 4 slender radial canals. Gonads oval or linear, their length very much varying; they are 

 placed along the radial canals, somewhat nearer to the circular vessel than to the manubriimi. 30 — 58 

 long tentacles with somewhat swollen basal bulbs. Usualh- 2 marginal vesicles between everv succes- 

 sive pair of tentacles, each vesicle containing one concretion. \'elum fairly narrow. Stomach, gonads, 

 and tentacular bulbs yellowish-brown or reddish-brown. 



Among the numerous species of Pliialidiiiiii described, two species are recorded as occurring in 

 the North-Atlantic area, viz. F^liialiditim heiiiispliwriciiiii (Gronovius), about 20 nun in diameter, with 

 up to 39 tentacles (according to Browne; as to the Icelandic specimens, see belowi, usualh' with 2 

 marginal vesicles between every successive pair of tentacles, and with linear, elongate gonads ou tiie 

 outer halves of the radial canals; and Pliialidiiiin buskiaiiiim (Gosse) Browne, up to 6 mm in diameter, 

 with 20 — 32 tentacles, with one, sometimes 2, marginal vesicles between every successive pair of tent- 

 acles, and with short, oval gonads between tlie middle of the radial canals and the circular vessel. 



I am very much inclined to think that these two species canr.ot be kept apart. liut the North- 

 Atlantic material at my disposal cannot serve as foundation for a discussion of the matter. The Zoo- 

 logical ]\Iuseum of Copenhagen possesses, however, a ver\- large material of [^hialidiiim from the 

 Danish waters and, moreover, a great many specimens, which I brought home from Plymouth in 1914- 

 I consider it most convenient, therefore, to postpone a thorough discussion of the variation of Pliiali- 

 diiiiti and the question of the limitation of the species, until that material b.as been further examined. 

 In the present paper I shall restrict nu'self to give .some information concerning the present 

 material. 



12* 



